1. Field of the Invention
This invention relates to a blood platelet preserving container and a method for the production thereof. More particularly, it relates to a blood platelet preserving container excelling in the blood platelet preserving ability and having no use for any embossing treatment and a method for the production thereof.
2. Description of the Prior Art
Generally, the inner sheet surface of a blood platelet preserving container is required to be as flat and smooth as permissible and for the purpose of ensuring favorable preservation of blood platelets and, at the same time, to be embossed for the purpose of preventing the sheet from blocking during the course of sterilization. In the production of a flat and smooth embossed sheet meeting the requirement, the operation of passing a blank sheet between the pressing surfaces of embossing rolls by the T-die extrusion molding or calendering process has been utilized during the molding of molten sheet into a sheet [Japanese Patent Laid-Open SHO 60(1985)-246,757 and Japanese Patent Publication SHO 57(1982)-6,946].
The embossing rolls which are required for the embossing treatment of this nature, however, are very expensive and necessitate a surface formed of a soft metal such as copper for the purpose of permitting impartation of an accurate shape. The surface of such a metal is liable to sustain a flaw readily. Even a slight injury impairs the surface condition of the produced sheet and exerts an adverse effect on the blood platelet preserving property. Thus, the product lacks uniformity of quality. The embossing rolls, therefore, must be renewed often, a fact which constitutes a serious economic drawback.
Further, since the sheet is passed between the pressing surfaces of rolls, it generates static electricity and consequently attracts dust, dirt, etc. and opens up the possibility of entraining foreign matter, the most serious problem for such medical containers as blood platelet bags.
Lusterless shaped articles produced by the embossing process are disclosed in Japanese Patent Laid-Open SHO 58(1983)-33,426, Japanese Patent Laid-Open SHO 58(1983)-152,040, Japanese Patent Laid-Open SHO 54(1979)-163,939, Japanese Patent Laid-Open SHO 56(1981)-142,025, Japanese Patent Laid-Open SHO 56(1981)-11,916, and Japanese Patent Laid-Open SHO 58(1983)-160,337, for example. A similar lusterless shaped article by the tubular film process for which the embossing rolls are unfit is obtained by cooling the die of a molding machine and the mandrel part as disclosed in Japanese Patent Laid-Open SHO 62(1987)-19,431. This method is generally adopted as means of preventing the phenomenon of blocking and improving the slipping property. Since these lusterless shaped articles have rough surfaces on the embosses embossed side, however, they have been generally regarded heretofore as unfit for preserving containers of blood, particularly blood platelets [as indicated in Japanese Patent Laid-Open SHO 54(1979)-86,967 and Cryogenic Medicine, Vol. 4, No. 1, pages 9-15 (1978)].
The idea of using a flexible vinyl chloride resin composition containing cross-linked vinyl chloride resin particles as medical materials is disclosed in Japanese Patent Laid-Open SHO 59(1984)-166,161 and U.S. Pat. No. 4,657,541, for example. It is intended exclusively for medical materials of the ordinary grade. The inventions do not specify this composition as to the particle diameter, the amount of addition, and other conditions of the crosslinked vinyl chloride resin particles in due consideration of their effects on the blood platelets.
An object of this invention, therefore, is to provide a novel blood platelet preserving container and a method for the production thereof.
Another object of this invention is to provide an economically excellent blood platelet preserving container endowed with a satisfactory surface property excelling in the blood platelet preserving ability by the molding process having no use for any expensive embossing rolls and having no possibility of entraining foreign particles and producing no adverse effects on the preservation of blood platelets and a method for the production thereof.